Alpine touring bindings allow the heel of the user's footwear (such as a ski boot) to be latched to a ski or other snow travel aid for sliding downhill (the “downhill mode”) and allow the heel to be released for walking and climbing (the “touring mode”). Thus, the binding allows for selective holding of the footwear heel to the snow travel aid so that the user may select between the downhill mode and the touring mode. Modern alpine touring bindings allow the footwear to release from the snow travel aid when in the downhill mode, in case of a fall. When in the touring mode, the user may climb or walk with a great degree of freedom since the footwear is pivotally engaged with the aid near the toe of the footwear while the heel of the footwear is free to move upward and downward relative to the aid. A historical collection of such bindings can be viewed in the “Virtual Museum of Backcountry Skiing Bindings” at www.wildsnow.com, authored by Louis Dawson.
Alpine touring bindings of the type that originated under the brand DYNAFIT are bindings that take advantage of the fact that modern alpine touring boots have a rigid sole. Thus, it is unnecessary to provide a bar, plate or other arrangement connecting toe and heel units, as is the case with many other alpine touring bindings (see patent publications EP0199098, EP0519243, EP1559457, and AT402020). This type of binding is referred to herein as a “Tech-type” binding.
Tech-type binding systems typically comprise a toe unit having a set of jaws that pivotally engage inserts in the footwear sole at the toe of the footwear. The toe unit is mountable at an appropriate location on the upper surface of a snow travel aid. A heel unit is mountable at a particular region on the upper surface rearward of the toe unit, the location of which is dictated by the length of the footwear sole. The toe and heel units function independently in retaining the footwear attached to the snow travel aid. The heel unit comprises one or more connectors (typically a pair of pins) which extend forward to engage a fitting placed in the rear of the footwear heel. Under forward release conditions during a fall, the pins are forced apart against spring pressure to respective release positions to disengage from the fitting and the heel. The pins typically communicate with a spring or springs through inclined sliding surfaces that move a block which engages the spring or springs.
The heel unit of a Tech-type type binding can facilitate lateral release in the case of a fall and allows transition to the touring mode as a result of the body of the heel unit being pivotally engaged on a generally vertical post. Variable release settings are provided by adjusting compression of a spring which forces a plunger against flat regions arranged around the circumference of the post on which the body rotates. The body of the heel unit will tend to stay in each rotational position corresponding to a flat region on the post, which facilitates retention of the heel unit in either the downhill or touring mode.
To switch between touring and downhill modes with such a system, it is necessary to rotate the heel unit so that the connector either engages the footwear heel (downhill position) or faces away from the heel (touring position). When the connector faces away, the footwear heel is free to move upward and downward to facilitate walking and climbing with the toe of the footwear pivotally retained on the snow travel aid by means of the toe unit. In order to switch from downhill mode to touring mode it is necessary to release the connector from the footwear heel first, whereupon the heel unit can be rotated to a touring position. This type of heel unit will occasionally rotate on its own from a touring position back to the downhill position as a result of snow build-up or jarring the binding. This can result in the heel unit becoming coupled to the footwear heel which interferes with touring. The device disclosed in EP0519243 compensates for this tendency by providing a one-way rotary coupling of the heel unit with a wedge member acting as a prominence that resists rotation in the opposite direction back to the downhill position.
Another Tech-type binding with a rotating heel unit is disclosed in U.S. 2015/0014963. That heel unit comprises an upper portion that is rotatable on a generally vertical axis between a downhill position and at least one lateral release position. The upper portion can rotate towards the lateral release position from the downhill position during a fall and is deliberately rotated to that position when the user places the binding in the touring mode. The upper portion comprises at least one camming surface such that rotation of the upper portion results in the at least one camming surface contacting a stop causing the upper portion to translate rearwardly away from the stop, against a force exerted by a forward biasing device. As disclosed in U.S. 2015/0014963, the upper portion can be releasably retained in the touring position against the force exerted by the forward biasing device by engagement of a detent in the camming surface with a fixed feature and/or by a part of the upper portion being engaged with a depression that is fixed relative to the upper portion. Such a depression may be behind a prominence over which a lobe on the upper portion rides when rotating to the touring position. Once the lobe is over the depression, weighting the apparatus by the user restricts the lobe from returning back over the ramp.